A process for producing a solid cast silicate-based cleaning compositions which includes the step of combining appropriate concentrations of an alkali metal silicate, an alkali metal hydroxide and a source of water to form a reaction mixture that solidifies into a reaction product which is processable at temperatures below the melting point or decomposition temperature of the reaction product. The process provides for the rapid manufacture of a solid cast alkaline cleaning composition without melting of the cast composition. Incorporation of appropriate amounts of a combination of a polyacrylate and a phosphonate into the cleaning composition cooperate with the silicate present in the composition to form a threshold system which is effective for controlling precipitation of both calcium and magnesium in a use solution.
The invention relates to solid, cast, silicate-based detergent compositions, methods of manufacturing such compositions, and threshold systems useful in such compositions. Specifically, the invention relates to methods of manufacturing substantially uniformly dispersed, solid, cast, silicate-based, alkaline detergent compositions which do not require xe2x80x9cmeltingxe2x80x9d of any component the reaction mixture or the reaction product and which can include an effective threshold system.
The advent of solid cast detergent compositions has revolutionized the manner in which detergents are dispensed by commercial and institutional entities which routinely use large quantities of cleaning solution. Prior to the advent of solid cast detergents, commercial and institutional entities were limited to either liquid, granular or pellet forms of detergent. However, because of the numerous unique advantages offered by solid cast detergents, the solid cast detergents, such as those disclosed in U.S. Pat. Nos. Re. 32,763, Re. 32,818, 4,680,134 and 4,595,520 quickly replaced the conventional liquid and granular detergents in the commercial and institutional markets.
The unique advantages offered by solid cast detergents include improved handling resulting in enhanced safety, elimination of component segregation during transportation and storage, increased concentration of active ingredients within the composition, and various others.
One method of manufacturing solid cast detergent compositions involves the steps of forming a homogenous melt of the detergent composition, casting the molten melt into a mold, and solidifying the melt by cooling.
Fernholz et al., U.S. Reissue Pat. No. 32,763 describes a method of manufacturing a solid cast detergent composition which involves the steps of (i) forming an aqueous solution of two hydratable chemicals, such as sodium hydroxide and sodium tripolyphosphate, (ii) heating the solution to a temperature of about 65xc2x0 to 85xc2x0 C., (iii) increasing the concentration of hydratable chemicals in the heated solution to produce a solution which is liquid at the elevated temperature but will solidify when cooled to room temperature, and (iv) casting the heated solution into molds for cooling and solidification.
While the solid cast detergents manufactured in accordance with the molten processes constitute a significant improvement over the previously known liquid and granular detergent compositions, the molten process is time consuming, requires large quantities of energy, and can result in deactivation of desirable operative cleaning components incorporated into the detergent such as bleaches, defoaming agents, enzymes, and tripolyphosphates if processing parameters are not closely monitored.
One effort to simplify and improve the molten process is disclosed in Copeland, et. al., U.S. Pat. No. 4,725,376 The Copeland patent describes a method of manufacturing a solid cast alkaline detergent composition capable of decreasing the extent of deactivation resulting from the manufacturing process. Briefly, the process disclosed by Copeland involves pouring an aqueous melt of a hydratable, alkaline, detergent component into a mold containing solid particles of a thermally-deactivatable detergent component such that the aqueous melt percolates through the interstitial void volume between the solid particles and-then solidifies to form a solid cast detergent composition containing homogeneously dispersed granules of the thermally-deactivatable detergent.
Gansser, U.S. Pat. No. 4,753,755, discloses a method for producing a solid alkaline detergent composition similar in mechanism to Fernholz et al.
Smith, U.S. Pat. No. 2,164,092, discloses a method for solidifying an aqueous alkaline solution by incorporating a metaphosphate into the alkaline solution under conditions capable of converting the metaphosphate to an orthophosphate and/or pyrophosphate with accompanying dehydration and solidification of the aqueous mixture.
While the processes disclosed by Gansser and Smith provide for the manufacture of solid cast detergent compositions, the process of Gannser additionally results in reaction mixtures which generally take several hours to solidify and require prolonged agitation to prevent segregation while the process of Smith is limited to phosphate-based detergents.
Accordingly, a substantial need exists for additional manufacturing techniques which can provide for the formation of solid cast detergent compositions without requiring the attainment of melt/decomposition temperatures.
The invention is broadly directed to a cast solid composition and methods for the production of solid cast silicate-based cleaning compositions which do not require melt phase processing. Specifically, the invention provides for the production of solid cast silicate-based cleaning compositions which rapidly solidify substantially simultaneously across the entire cross section of the reaction product. In the process, as a result of mixing and under conditions of mixing, a thermodynamically unstable liquid mixture is formed that can rapidly solidify into a thermodynamically stable solid. Because the cleaning composition includes silicate as the source of alkalinity, a synergistically effective threshold system may be incorporated into the composition for the purpose of preventing the precipitation of both calcium and magnesium ions.
The process combines appropriate concentrations of an alkali metal silicate or mixtures of silicates, an alkali metal hydroxide and a source of water to create a liquid or fluid reaction mixture which is processable at temperatures below the melting point or decomposition temperature of the reaction product and which forms a reaction product which is solid under processing conditions.
The product of the process of the invention typically comprises a hydrated silicate containing composition or mixtures of a hydrated silicate species thereof. The hydrated silicate materials can contain additional amounts of concentrated sodium hydroxide as part of the solid matrix. In the solidification processes involved in the invention, a silicate composition, optionally another silicate species, and sodium hydroxide, interact with a wash chemical to form a liquid reaction mixture that is thermodynamically unstable which becomes thermodynamically stable through a solidification process. In the solidification process, the materials react to alter the normaly fluid constituent ratios to different ratios that are normally solid at ambient temperatures. In such reactions, we have found that most processing mixtures with common ratios of ingredients, that two or more discrete hydration states are formed in the reaction product. We have found that the production of two or more hydration states can be characteristic of products made with this reaction. It should be understood that at certain xe2x80x9cperfectxe2x80x9d ingredient ratios, single hydration states can be formed. However, under most processing conditions and combinations of ingredients, two, three or more, discrete hydration states can be formed. Such hydration states can be identified using differential scanning calorimetry (DSC) wherein each hydration has its characteristic temperature on a DSC curve, each hydration having a peak in the curve at differing temperatures.
Definitions
As used herein, including the claims, the term xe2x80x9cambientxe2x80x9d refers to those temperatures (about 10xc2x0 C. to about 50xc2x0 C.) and pressures (about 700 to 900 mm Hg) typically encountered in the environment.
As used herein, including the claims, the term xe2x80x9ccleaning compositionxe2x80x9d refers to multiple component substances which are useful in cleaning surfaces and substrates.
As used herein, including the claims, the term xe2x80x9ccleaning solutionxe2x80x9d refers to an aqueous solution containing a sufficient quantity of a cleaning composition to be effective for cleaning surfaces and substrates.
As used herein, including the claims, the term xe2x80x9cwash chemicalxe2x80x9d or xe2x80x9coperative cleaning componentxe2x80x9d refers to components which can enhance the cleaning ability of a cleaning composition. Operative cleaning component includes specifically, but not exclusively: sources of alkali such as an alkali metal hydroxide, an alkali metal silicate, anti-redeposition agents, bleaches, enzymes, sequestrants, surfactants, and threshold agents or systems. When used in the claims, a wash chemical, when combined with a first form of silicate, refers to a second different silicate composition or form. In other words, the different silicate is a silicate that differs in Na2O:SiO2 ratio.
As used herein, including the claims, the terms xe2x80x9cdeactivatexe2x80x9d and xe2x80x9cdeactivationxe2x80x9d refer to a reduction or elimination in a useful chemical property or characteristic through chemical modification.
As used herein, including the claims, the term xe2x80x9cmelting point or decomposition temperaturexe2x80x9d, refers to the temperature at which a solid substance begins to melt or decompose the hydrate e.g. evaporate or drive off water. The solid silicate systems of this invention are considered to possess a melt temperature if they pass from a solid to a liquid at a temperature below the boiling point of water such that the water portion of the composition remains in the heated composition and are considered to possess a decomposition temperature if they melt at a temperature above the boiling point of water such that the water portion of the composition leaves the heated composition as stem.
As used herein, including the claims, the term xe2x80x9cexternally supplied heatxe2x80x9d refers to the intentional addition of heat to a system from a separate and independent heat source such as steam and specifically excludes the addition of heat to a system caused by variances in ambient conditions and exothermic reactions occurring between reactants in the system.
As used herein, including the claims, the term xe2x80x9cformulationxe2x80x9d refers to the chemical composition or constitution of a substance. The formulation of a mixture is defined by the amount and composition of each ingredient.
As used herein, including the claims, the term xe2x80x9cprocessablexe2x80x9d means having sufficient fluidity or sufficiently low viscosity to be stirred, mixed, agitated, blended, poured, and/or molded in common industrial mixing equipment.
As used herein, including the claims, the term xe2x80x9cprocess conditionsxe2x80x9d refers to the product temperatures and pressures encountered during processing.
As used herein, including the claims, the term xe2x80x9creaction mixturexe2x80x9d refers to a mixture of reactants prior to conversion of a meaningful proportion of the reactants to a reaction product.
As used herein, including the claims, the term xe2x80x9cmeaningful proportionxe2x80x9d, when used in connection with xe2x80x9creaction mixturexe2x80x9d, means a proportion sufficient to perceptibly alter the physical characteristics of the mixture or to introduce a desirable cleaning property to the cast material such as detergency, hardness sequestering, soil anti-redeposition, etc.
As used herein, including the claims, the term xe2x80x9creaction productxe2x80x9d refers to the composition resulting from completion of the solidification of a reaction mixture.
As used herein, including the claims, the term xe2x80x9croom temperaturexe2x80x9d refers to the temperature typically maintained in an environmentally controlled living space (about 15xc2x0 C. to about 32xc2x0 C.).
As used herein, including the claims, the term xe2x80x9csolidxe2x80x9d refers to a substance which will not flow perceptibly under moderate stress. Specifically, a cast substance is deemed to be xe2x80x9csolidxe2x80x9d when the substance will retain the shape of the mold when removed from the mold.
As used herein, including the claims, the term xe2x80x9cstoichiometric excessxe2x80x9d refers to an amount of a chemical reactant which exceeds that necessary to convert all other reactants to product based upon the quantitative chemical relationship of the reactants. For example, a combination of 10 moles of hydrogen and 4 moles of oxygen to form H2O includes a stoichiometric excess of 2 moles of hydrogen.
As used herein, including the claims, the term xe2x80x9csupercooledxe2x80x9d refers to a condition of thermodynamic instability caused by the existence of a liquid system at a temperature below the freezing point of that system.
As used herein, including the claims, the term xe2x80x9cthermodynamic stabilityxe2x80x9d refers to a condition of thermodynamic equilibrium.
As used herein, including the claims, the term xe2x80x9cthermodynamically unstablexe2x80x9d refers to a thermodynamic situation where either the physical or chemical state of a liquid system has not achieved thermodynamic equilibrium and the instability created by mixing liquid components is released by the solidification of the unstable liquid, and the gain or loss of a heat of solidification.
As used herein, including the claims, the term xe2x80x9cthreshold agentxe2x80x9d or xe2x80x9cthreshold systemxe2x80x9d refers to those compounds or combination of compounds which exhibit the ability to prevent the precipitation of hardness ions from an aqueous system at a concentration which is significantly less than the concentration of hardness ions in the aqueous system.
As used herein, the term xe2x80x9cwt % waterxe2x80x9d refers to all water contained in the composition and specifically includes both free and chemically bound water regardless of source.
As used herein, the term xe2x80x9cwt %xe2x80x9d is based upon the amount of alkali metal silicate, alkali metal hydroxide and water in the reaction mixture unless otherwise specified.